Dehydrogenation process



United States Patent 3,450,787 DEHYDROGENATION PROCESS William L. Kehland Raymond J. Rennard, Jr., Pittsburgh, Pa., assignors to Goodrich-GulfChemicals, Incorporated, Cleveland, Ohio, a corporation of Delaware NoDrawing. Filed May 21, 1968, Ser. No. 730,916 Int. Cl. C07c /18 U.S. Cl.260680 22 Claims ABSTRACT OF THE DISCLOSURE Process for the oxidativedehydrogenation of hydrocarbons which comprises contacting a mixture ofa hydrocarbon and oxygen with a magnesium chromium ferrite catalyst at atemperature above about 250 C., thereby producing a dehydrogenatedhydrocarbon having the same number of carbon atoms as said hydrocarbon.

BACKGROUND OF THE INVENTION Field of the invention This inventionrelates to a process for dehydrogenating hydrocarbons. Moreparticularly, this invention relates to the oxidative dehydrogenation ofhydrocarbons in the presence of oxygen and a catalyst.

DESCRIPTION OF THE PRIOR ART Oxidative dehydrogenation processes havebeen employed to convert saturated and/or unsaturated hydrocarbons tomore highly unsaturated hydrocarbons through removal of hydrogen fromsuch hydrocarbons by combination with oxygen to form water and theunsaturated product in the presence of a catalyst. Catalyst systems haveheretofore been proposed to increase the selectivity of the process toproduce the desired product and the conversion per pass of the feedstream thereby maximizing the yield per pass of the desired product.Many of these catalysts, however, have necessitated the use ofrelatively high reaction temperatures, e.g., above 600 C., and/or lowpressures, generally between about 5 and 25 p.s.i.a. Recently, catalystsof the ferrite family have been proposed for use in oxidativedehydrogenation processes. These catalysts, however, are prepared atrelatively high temperatures, i.e., about 850 C. to 1,300" O, and havebeen found to be stable for only relatively short periods of time atreaction conditions.

Accordingly, it is an object of the present invention to provide acatalyst system which when employed in oxidative dehydrogenationprocesses effects high conversion and selectivity to the desiredproduct.

It is another object of the present invention to provide a more stableand hence longer lived catalyst system than heretofore employed inoxidative dehydrogenation processes.

It is still another object of the present invention to provide anoxidative dehydrogenation process employing relatively low reactiontemperatures and being essentially free of pressure limitations.

SUMMARY OF THE INVENTION In accordance with the present invention, aprocess is provided for the oxidative dehydrogenation of hydrocarbonscomprising contacting a mixture of a hydrocarbon 3,450,787 Patented June17, 1969 containing at least about 4 carbon atoms and oxygen with amagnesium chromium ferrite catalyst having the empirical formula Mg CrFe Q, wherein a ranges from about 0.1 to about 3, b ranges from greaterthan 0 to less than 2 and c ranges from greater than 0 to less than 3,at a temperature above about 250 C. thereby producing a dehydrogenatedhydrocarbon having the same number of carbon atoms as said initialhydrocarbon.

DESCRIPTION OF THE INVENTION The catalysts useful in the presentinvention are magnesium chromium ferrites containing, as the activecomponents thereof, magnesium, chromium and iron cations in a singlephase partially inverted spinel compound. Mag nesium has a strongeroctahedral site stabilization energy than the trivalent iron, and whenthese are combined in accordance with the present invention, the resultis a partially inverted spinel in which a significant number of themagnesium cations tend to occupy octahedral sites and a correspondingnumber of iron cations are displaced into tetrahedral sites. Thecatalyst can be employed in the form of the homogeneous magnesiumchromium ferrite, per se, or as a heterogeneous composition containing amixture of the oxides of said cations and the single phase partiallyinverted spinel compound.

The catalyst employed in the present invention can be represented by theempirical formula Mg Cr Fe O wherein a can vary within the range ofabout 0.1 to about 3, b can vary from greater than 0 to less than 2 and0 can vary from greater than 0 to less than 3. In a preferred form ofthe catalyst a can vary within the range of about 0.1 to about 2.0, bcan vary from about 0.1 to about 1.8 and 0 can vary from about 0.25 toabout 1.9 while in a more preferred arrangement a can vary from about0.8 to about 1.3, b can vary from about 0.2 to about 1.5 and c can varyfrom about 0.5 to about 1.8. In the most preferred form of the catalysta is about 1.0.

In the homogeneous structure all of the elements are located in a singlephase magnesium chromium ferrite compound. Since magnesium possesses ahigh octahedral site stabilization energy, a substantial amount of themagnesium will be in octahedral sites and a corresponding amount of ironwill be in tetrahedral sites. Since localized irregularities andnon-stoichiometric relationships will occur in the lattice ofhomogeneous magnesium chromium ferrite as actually prepared, a is about1.0 and the sum of b+c is about 2.0.

In the heterogeneous composition, also represented by the empiricalformula Mg Cr Fe O there will be present the single phase magnesiumchromium ferrite compound as well as one or more oxides (or combinedoxides) of one or more of the constituent cations. For example, if inthe empirical composition a is about 3, the catalyst will contain amajor amount of magnesium oxide and a minor amount of a magnesiumchromium ferrite compound. In this instance the composition will possesscatalytic activity due to the magnesium chromium ferrite compound withmagnesium oxide serving essentially as an inert diluent. Chromium andiron oxides, if present, may not be inert, i.e. they will have someactivity for the desired reaction but with lower selectivity to thedesired reaction. The empirical composition MgCrFeO, can represent ahomogeneous composition or it can be a heterogeneous mixture of amagnesium chromium ferrite and individual oxides.

The homogeneous material can only result when a is 1.0 or about 1.0.When a deviates significantly from 1.0, the material is heterogeneous.

The magnesium chromium ferrite catalysts of the present invention can beidentified by their characteristic X- ray diffraction patternsillustrative of which is that for MgCrFeO which consists of lines withthe following d spacings and relative intensities d(A I/I 4.83 36 2.9624 2.52 100 2.41 5 2.09 35 1.705 1 1.605 30 1.475 40 The relativeintensities and the width or sharpness of the lines in the patterns fromthese compounds will vary with changes in the relative concentrations ofthe cations in the structure. Inhomogeneity in the catalyst compositionsis manifested by additional or doubled lines in the pattern.

The magnesium chromium ferrites can be conveniently prepared byemploying as starting materials salts of magnesium, chromium and iron,in which salts the metals are contained as cations. Any such salt ofsaid metals is satisfactory, however, it is preferred to employinorganic salts of the metals, such as, for example, nitrates,carbonates, acetates and halides. These salts containing the metals ascations are then admixed with a basic reactant in order to precipitatethe precursor of the final product. It is necessary to maintain thisaddition mixture at a high pH-above about 8, and preferably above about9. It is considered preferable to vigorously stir the metal salts inorder to reduce any pH gradients through said addition mixture.

In Order to prevent the inclusion in the precursor, and thus in thefinal product, of any contaminant it is essential that either avolatilizable base or a base containing no deleterious contaminants suchas, for example, sodium, be employed. Any base which can be vaporizedreadily under the conditions used for drying and calcining can beemployed, such as, for example, ammonium carbonate, ammonium bicarbonateand ammonium hydroxide. It is considered preferable, however, to employan aqueous ammonia solution as the volatilizable base.

After precipitation, advantageously the precursor is washed, again at apH above about 8, and preferably above about 9, and then dried andcalcined. This drying and calcining can effectively be accomplished byany of the techniques well known in the art. Generally, drying can beaccomplished at temperatures from about 100 C. to about 150 C. for aperiod of from about 4 to about 60 hours while calcining can be effectedat temperatures ranging from about 350 C. to about 800 C. for a periodof from about 2 to 16 hours.

It has been found that the catalysts of the present invention can beconveniently prepared by forming aqueous solutions of salts of therespective cations, magnesium, chromium and iron, preferably the nitratesalts thereof, and admixing said solutions with an aqueous ammoniumhydroxide solution at a pH above about 8, preferably between a pH offrom about 8.5 to about 8.9, thereby co-precipitating the hydroxides ofthe cations. The resulting precipitate can then be washed, filtered,dried and calcined to yield the finished bulk catalyst.

The catalyst can be employed with or without a filter or carriermaterial and can be pelletized or formed employing conventionaltechniques. Suitable carrier materials are, for example, rough granularaluminas, zirconias, granular silicon carbide and other similar inertmaterials. Supported catalysts can be prepared by thoroughly mixing thegranular particles of the carrier 4 material with a thick wet slurry ofthe washed mixture of combined precipitates prior to drying andcalcining. The slurried mixture can thereafter be dried at about 120 C.and calcined at about 650 C. to provide granular particles of thesupported catalyst.

The process of the present invention is useful in the dehydrogenation ofhydrocarbons containing at least four carbon atoms. Preferably,aliphatic and aromatic hydrocarbons are employed such as, for example,monoolefins, cycloaliphatic hydrocarbons, aromatic hydrocarbons andmixtures thereof. Exemplary of such hydrocarbons are butene-1,cis-butene-Z, trans-butene-2, 2- methyl butene-3, 2-methyl butene-1,Z-methyl butene-2, cyclohexene, Z-methyl pentene-l, Z-methyl pentene-Z,normal amylenes, other isoamylenes, and the like and mixtures thereof.For example, the process of the present invention is useful inconverting butene to butadiene-1,3. Still further, the process can beemployed to convert normal amylenes to piperylene or isoamylenes toisoprene. Thus, it can be seen that the process of the present inventionis, in general, useful in converting unsaturated hydrocarbons tohydrocarbons of greater unsaturation.

The feed streams can be mixed hydrocarbon streams such as refinerystreams or effluents from thermal or catalytic cracking processes. Theseand other refinery byproduct streams Which contain normal hydrocarbonsand/or ethylenically unsaturated hydrocarbons are useful feed stocks.

It has been found, for example, that a mixed feed stream containingbutene and butane can result in butene conversions of greater than 50mole percent with greater than percent selectively to butadiene-1,3. Ithas been found that little or not butane was converted to water andcarbon dioxide thereby leaving essentially intact the oxygen needed forthe oxidative dehydrogenation of butene to butadiene. Thus, the processof the present invention can, as an embodiment thereof, be employed as atwo-stage process wherein a first stage butane is nonoxidativelydehydrogenated to a butane-butene mixture over a suitable catalyst suchas, for example, chromia on alumina, and the butene in the resultingmixed effluent stream is converted to butadiene-1,3, in accordance withthe present invention, in a second stage.

Oxygen is fed to the reaction zone in an amount ranging from about 0.2to about 2.5 moles of oxygen per mole of hydrocarbon to bedehydrogenated. Preferably, about 0.3 to about 1 mole of oxygen per moleof hydrocarbon is employed. In general, it has been found that as theamount of hydrocarbon being fed to the reaction zone is increasedrelative to the oxygen, the conversion decreases and, to a lesserdegree, the selectivity increases, with the result that the yield of thedesired product decreases as the oxygen to hydrocarbon ratio decreases.The oxygen can be fed to the reaction as pure oxygen, air,oxygen-enriched air, oxygen mixed with inert diluents and the like. Thetotal amount of oxygen utilized can be introduced into the gaseousmixture entering the reaction zone or can be added in increments atdifferent sections of the reaction zone.

The conversion of the feed stream can be increased by employing a seriesof reaction zones with provision to introduce additional oxygen betweenreaction zones. The points of introduction of the additional oxygen areestablished to insure that any unreacted hydrocarbon can react over anarea of active catalyst after the supply of oxygen in the initial feedstream has been substantially exhausted. It is important, however, thatthe added oxygen be intimately admixed with the other gases and vaporsin the reaction zone prior to exposure of the oxygen-enriched mixture toan area of active catalyst.

The hydrocarbon feed stream is preferably dehydrogen-ated in thepresence of added steam; however, the use of steam is not essential andcan be omitted. When employed, it is considered preferable that thereaction mixture contain a quantity of steam ranging from about 5 toabout 30 moles of steam per mole of hydrocarbon to be dehydrogenated andmost preferably from about to about moles of steam per mole ofhydrocarbon. In addition to acting as a diluent in the process, the fiowrate and inlet temperature of the steam can be regulated to vary theinternal reaction temperature.

The dehydrogenation reaction proceeds at temperatures of at least about250 C. Preferably, the reaction is conducted at temperatures betweenabout 300 C. and about 500 C. although higher temperatures approaching600 C. or higher can be employed if desired. It is consideredadvantageous to operate at the lower end of the temperature range, forexample, from about 250 C. to about 350 0, since the amount of carbondioxide produced at these temperatures is appreciably less than athigher temperatures.

The dehydrogenation reaction can be conducted at atmospheric pressure,superatmospheric pressure or subatmospheric pressure. The total pressureof the system will normally be about or in excess of atmosphericpressure but generally below 10 atmospheres to avoid the explosive limitof the feed stream. Generally the total pressure will range from about0.7 to about 10 p.s.i.g. Preferably the total pressure will be in therange of about 0.7 to 5 p.s.i.g. Excellent results have been obtained atabout atmospheric pressure.

The process of the present invention can be satisfactorily conductedover a wide range of flow rates. The optimum flow rate is dependent uponthe reaction temperature, pressures, catalyst particle size and type ofreactor employed, e.g., fluid bed or fixed bed. The gaseous hourly spacevelocity (GHSV) as used herein is the volume of the total hydrocarbonfeed in the form of vapor calculated under standard conditions oftemperature and pressure C. and 760 mm. Hg) passed per hour per unitvolume of catalyst. Generally, the GHSV will be between about 200 toabout 6,000 with GHSV between about 450 and 2,000 considered mostpreferable.

The dehydrogenation reaction zone can be of the fixed bed or fiuid bedtype. Conventional reactors for the production of unsaturatedhydrocarbons are satisfactory. The reactor can either be packed withparticular catalyst, per se, or the catalyst can be deposited on acarrier or support medium as hereinabove described. Other methods cansimilarly be employed to introduce the catalyst into the reaction zone;for example, the reaction zone itself can be coated with the catalyst orthe catalyst in the form of wires, mesh, shreds, tablets and the likecan be packed within the reactor.

Although not essential, the catalysts employed in the present inventioncan be activated by oxidizing and reducing the catalysts in the folowingsequence: Catalyst is oxidized by passing a stream containing about onepart oxygen to about four parts inert diluent such as steam, helium,nitrogen and the like, over the catalyst at temperatures between about400 C. to 600 C., preferably about 500 C. for about minutes. Thereafter,a feed stream comprised of steam, hydrocarbon and oxygen is passed overthe catalyst in a gas volume ratio of about 10/1/1, respectively,although the amount of each component can be varied without adverseeffect. The feed stream is passed over the catalyst at temperatures ofabout 300 C. to 500 C., preferably at 400 C., for about 30 minutes.Thereafter, the oxidation step is repeated as described above, followedby reaction with the feed stream described above having a gas volumeratio of about 30/3/ 1, respectively, although again this ratio can bevaried Without adverse effect. The oxidation step described hereinaboveis again repeated and finally the catalyst is reduced through use of anyreducing gas such as hydrogen, carbon monoxide or hydrocarbons. Mostconveniently a hydrocarbon such as butene can be employed as thereducing agent particularly in instances wherein butene is thehydrocarbon to be dehydrogenated simply by stopping the flow of oxygen.Thus, reduction of the catalyst is accomplished by passing butene orother similar hydrocarbon reducing gas in an inert diluent such assteam, helium and the like over the catalyst at temperatures betweenabout 400 C. to 600 C., preferably at about 500 C., for about 30minutes. Thereafter, the active catalyst of the present invention isobtained, providing higher conversion and selectivity to the desiredunsaturated hydrocarbon together with lower isomerization activity. Thissuperior performance is maintained at temperatures as low as about 325C. with the additional advantage that the amount of carbon dioxideproduced is less at such low temperatures than at the highertemperatures.

EXAMPLES The following examples are to further illustrate the presentinvention and should not be considered as imposing any limitations onthe scope of the invention. Unless otherwise specified, all percentagesand parts are by weight.

EXAMPLE 1 A magnesium chromium ferrite catalyst was prepared in thefollowing manner: 76.8 gm. of Mg(NO -6H O, and were dissolved in 1,000ml. of distilled water forming a mixed cation solution. 250 ml.concentrated NH OH was added to 750 ml. of distilled water forming abase solution. The base solution was added to a vessel containing 1,000ml. of distilled water until a pH of 8.0 was attained. Thereafter, themixed cation solution and the base solution were simultaneously, slowlyadded to the vessel with vigorous stirring, adjusting the rate ofaddition of the base solution to maintain a pH of 8.5 to 9.0 in thevessel. The final pH was between 8.9 to 9.0. The time required for thesimultaneous addition was about 30 minutes, and a volume of 720 ml. ofthe base solution was employed. The resulting precipitate was allowed tosettle overnight, and the clear supernatant liquid was thereafterdecanted. Additional water was added and the decantation procedurerepeated until the precipitate had been washed with at least two orthree complete changes of water. The washed precipitate was filtered,dried at C. and calcined at 650 C. for 16 hours.

X-ray diffraction analysis of the calcined product in tures within thecatalyst bed were determined by meansof a 34 concentric stainless steelthermocouple will running the length of the reactor. The void spaceabove and below the catalyst bed was filled with coarse particles ofsilicon carbide. The first 5" of the reactor were used to preheat theinlet gases to reaction temperatures.

The catalyst was activated by oxidizing the catalyst with a 1.5/1mixture of helium and oxygen for 30 minutes at 500 C. at a total GHSV of1,500 hr.- The catalyst was further conditioned by reaction at 400 C.with a feed stream consisting of a 10/ 1/ 1 mixture based on a gasvolume of steam, butene-2 and oxygen. The reaction was carried out for30 minutes at a total GHSV of 5,500 hl'f After the reaction, thecatalyst was reoxidized as described above and thereafter the reactionwas continued at 400 C. with a 30/ 3/ 1 mixture based on gas volume ofsteam, butene-2 and oxygen. The reaction was conducted for 30 minutes ata total GHSV of 4,200 hr.- The catalyst was again oxidized as describedabove and then reduced at 500 C. with a 10/1 mixture of heliiun andbutene-2 for 30 minutes at a total GHSV 7 of 5,000 biz- Although theoxidation and reduction steps described herein have been conducted withhelium as the inert diluent nitrogen, steam, or any other similar inertdiluent can likewise be employed.

The results obtained with the catalyst prior to activa- What is claimedis:

1. Process for the oxidative dehydrogenation of hydrocarbons comprisingcontacting at least one hydrocarbon containing at least about 4 carbonatoms and oxygen with a magnesium chromium ferrite catalyst having theempirition and after activation are summarized in Table l 5 cal formulaMg Cr Fe O wherein a ranges from about below. 0.1 to about 3, b rangesfrom greater than to less than TABLE 1.PRIOR To ACTIVATION Feed StreamYield of Conver- 04115 CO: Butadiene Steam/ GHSV sion (Mole (Mole (Mole(Mole '1. C.) 04/0 Butene (Butene) Percent) Percent) Percent) Percent)400-. 1 10 450 54 72 28 39 400.. 0. 33 10 450 19 72 28 14 AFTERACTIVATION 350-. 1 10 450 77 30 20 61 400 1 10 450 79 s2 18 65 400 0. 5450 51 90 10 46 350 1 10 450 76 36 14 65 350 0. 67 10 450 64 90 10 53325 1 10 450 s2 s4 16 69 325 0. 67 10 450 61 90 10 55 325 1 450 80 86 1469 325 0. 67 20 450 41 92 8 33 325 0. 67 14 675 65 90 10 53 325 0. 67 10900 76 91 9 69 325 0. 67 s 1, 125 75 33 12 66 325 0. 67 7 1, 350 70 3s12 62 325 o. 67 17 1, 350 71 90 10 64 400 1 10 450 7s s2 18 64 EXAMPLE 22 and c ranges from greater than 0 to less than 3, at a To furtherillustrate the superior performance of the temperature above about yProducing a magnesium chromium ferrite compositions employed indobydrogenated f o at havlug the Same number of the present invention,the oxidative dehydrogenation carbon atoms as Sald lultlat hydrocarbon;process as described herein was conducted employing rocess as'dofiuedolalm 1 Wbefolu t o magueslum difierent magnesium chromium ferritecompositions and, cbromlum terflto Catalyst has the omplfloal formulafor comparative purposes, oxides of the cations employed a b c 4 Wberolua ranges from about to about in the present invention. Table 2 shownbelow summarizes b g s from a ut 0.1 t about 1.8 and c ranges theresults obtained employing the catalysts of the presfrom about 0.25 toabout 1.9. ent invention and magnesium ferrite, magnesium chromite, 3.Process for the oxidative dehydrogenation of hydroiron chromite andferric oxide. carbons comprising contacting at least one hydrocarbonTABLE 2 Con- Yield version Cilia CO: 04116 Catalyst Composi- (Mole (Mole(Mole (Mole tion '1. C.) Oz/OJI Percent) Percent) Percent) Percent) 4001 79 32 1s MgCrFcOl 400 0. 5 51 90 10 46 325 0.67 64 90 10 58 400 1 6715 57 l\lgCr Fe O 400 0. 5 38 36 14 33 325 0.67 44 85 15 37 400 1 46 8416 37 MgFeaO 400 0. 5 26 10 24 325 0.67 7 3.; 6 400 1 9 11 Macho 400 0.5 16 42 5s 7 400 1 41 62 3s 25 400 0.33 26 35 15 22 FGCIOQ 400 1 55 7624 42 400 0. 50 36 85 15 31 400 0.33 30 87 13 26 400 1 34 55 45 19 4009.33 12 61 39 7 F6203 400 1 31 56 44 17 400 0.50 19 57 43 11 400 0.33 1252 4s 6 EXAMPLE 3 55 containing at least 4 carbon atoms and from about0.2 to The following example illustrates the elfect of the conaboutmolos of y u P l of Sald hydrocarbon joint use of n-butane in theoxidative dehydrogenation of ba maguoslum obrouuum fomto a l havlug thobutene-Z to butadiene employing the magnesium chroempulcal formula a b c4 Wbofolll a ranges from mium ferrite catalyst of the present invention.The procabout to about b ranges from about to about ess employed wassubstantially similar to that described 0 and c ranges from about toabout at a in Example 1, except that the feed stream contained acombined butane-butene stream. The results obtained are summarized inTable 3 below.

perature above about 250 C., thereby producing a dehydrogenatedhydrocarbon having the same number of carbon atoms as said initialhydrocarbon.

TABLE 3.EFFECT OF n-BUTANE ON THE OXIDATIVE DEHYD RO GENATION OF BUTENETO BUTADIENE Selectivity Yield Conversion to CH6 CO6 C4H5 Butane]Oxygen] (Mole (Mole (Mole (Mole Catalyst Composition '1. C.) ButeneButene Percent) Percent) Percent) Percent) 400 0 l 66 81 19 53 C1 .Fe O325 15 46 Mg H 4 325 1 0.67 53 90 10 43 325 3 0. (i7 23 92 8 21.

- Steam/C H;=13.5/1.

4. Process as defined in claim 3 wherein the mixture additionallycontains from about to 30 moles of steam per mole of hydrocarbon.

5. Process as defined in claim 3 wherein the oxidative dehydrogenationis conducted at temperatures of from about 300 C. to about 500 C.

6. Process as defined in claim 3 wherein the magnesium chromium ferritecatalyst has the empirical formula Mg Cr Fe O wherein a ranges fromabout 0.8 to about 1.3, b ranges from about 0.2 to about 1.5 and cranges from about 0.5 to about 1.8.

7. Process for the oxidative dehydrogenation of hydrocarbons whichcomprises contacting at least one hydrocarbon containing at least 4carbon atoms, from about 0.2 to about 2.5 moles of oxygen per mole ofhydrocarbon and from about 5 to about 30 moles of steam per mole ofhydrocarbn with an activated magnesium chromium ferrite catalyst havingthe empirical formula Mg Cr Fe O wherein a ranges from about 0.1 toabout 3, b ranges from greater than 0 to less than 2 and c ranges fromgreater than 0 to less than 3, at temperatures above about 250 C.,thereby producing a dehydrogenated hydrocarbon having the same number ofcarbon atoms as said initial hydrocarbon.

8. Process as defined in claim 7 wherein the hydrocarbon is butene.

9. Process as defined in claim 7 wherein the hydrocarbon streamcomprises a mixture of butene and butane.

10. Process as defined in claim 7 wherein the hydrocarbon is anisoamylene.

11. Process as defined in claim 7 wherein the mixture contains fromabout 0.3 to about 1 mole of oxygen per mole of hydrocarbon.

12. Process as defined in claim 7 wherein the mixture contains fromabout 10 to about 20 moles of steam per mole of hydrocarbon.

13. Process as defined in claim 7 wherein the oxidative dehydrogenationis conducted at temperatures of from about 300 C. to about 500 C.

14. Process as defined in claim 7 wherein the magnesium chromium ferritecatalyst has the empirical formula MgCr Fe O wherein b+c=about 2.

15. Process as defined in claim 7 wherein the magnesium chromium ferritecatalyst has the empirical formula MgCrFeO 16. Process for the oxidativedehydrogenation of hydrocarbons comprising:

(a) contacting a magnesium chromium ferrite catalyst having theempirical formula Mg Cr Fe O wherein a ranges from about 0.1 to about 3,b ranges from greater than 0 to less than 2 and c ranges from greaterthan 0 to less than 3, with an oxidizing stream comprising oxygen and aninert diluent at temperatures of from about 400 C. to about 600 C. for aperiod of time suflicient to oxidize said catalyst;

(b) passing a feed stream of steam, hydrocarbon and oxygen over thecatalyst at temperatures of from about 300 C. to about 500 C. for atleast about 30 minutes;

(c) reoxidizing the catalyst as in (a);

(d) passing a feed stream over the catalyst as in (b);

(e) reoxidizing the catalyst as in (a); p

(f) reducing the catalyst by passing a reducing stream over the catalystcomprising a reducing gas and an inert diluent at a temperature of fromabout 400 C. to about 600 C. for at least about 30 minutes; andthereafter,

(g) contacting at least one hydrocarbon containing at least 4 carbonatoms and from about 0.2 to 2.5 moles of oxygen per mole of hydrocarbonwith said activated magnesium chromium ferrite catalyst at a temperatureabove about 200 C., thereby producing a dehydrogenated hydrocarbonhaving the same number of carbon atoms as said initial hydrocarbon.

17. Process as defined in claim 16 wherein the reactant mixtureadditionally contains from about 5 to about 30 moles of steam per moleof hydrocarbon.

18. Process as defined in claim 16 wherein the magnesium chromiumferrite catalyst has the empirical formula Mg Cr Fe O wherein a rangesfrom about 0.1 to about 2, b ranges from about 0.1 to about 1.8 and cranges from about 0.25 to about 1.9.

19. Process as defined in claim 16 wherein the hydrocarbon is butene.

20. Process as defined in claim 16 wherein the hydrocarbon streamcomprises a mixture of butene and butane.

21. Process as defined in claim 16 wherein the hydrocarbon is anisoamylene.

22. Process as defined in claim 16 wherein the reducing gas is butene.

References Cited UNITED STATES PATENTS 3,284,536 11/1966 Bajars et a1.260-680 PAUL M. COUGHLAN, IR., Primary Examiner.

US. Cl. X.R. 252468 Notice of Adverse Decision in Interference InInterference N0. 97 ,358 involving Patent No. 3,450,787, L. Kehl and R.J. Rennard, J12, DEI-IYDROGENATION PROCESS, final judgment adverse tothe patentees was rendered Oct. 7, 1974:, as to claims 1, 3, 5, 7 8 and10-13.

[Offioial Gazette February 18, 1975.]

